Moon Lake –
Oxbow
Moon lake is a crescent shaped lake located
approximately 14
Kilometres (8.7 miles) south west of the city of Saskatoon,
Saskatchewan, Canada. It is a typical oxbow
lake formation and was
formed by glacial action and “meandering
river” dynamics in this
portion of the South Saskatchewan river basin. The lake today is approximately
150 meters wide and 5
kilometres in arc length. It is totally isolated from the
present South
Saskatchewan river and is fed by natural drainage from the north west as
well as irrigation canals from the existing South Saskatchewan
river. The lake is
home to a variety of wildlife and waterfowl.
Approximately c. 95,000 and c. 20,000 years
before the present day this area of Saskatchewan was covered by
the Laurentide ice
sheet. With the passage of time
and gradual warming (Global warming) the glaciers underwent periods
of melting. Advancing
and retreating with the fluctuations of temperature. The South Saskatchewan River basin
was the natural drainage system for the glacial melt waters and
carried vast amounts of water north easterly draining into
ancient Lake
Agassiz . The original river basin at this
location extended from Moon Lakes NW bank to the SE bank located at
the Beaver Creek conservation area. A distance of approximately 6 Kilometers
(3.7 miles). It was almost large enough to be
considered a small lake.
The first step in the creation of Moon lake was the
existence of a large whirlpool on the west bank of the river
basin. Huge chunks of
glacial ice slowly moved in a circular eddy dragging bottom and
deepening the river bottom. As the water levels receded huge
chunks of ice grounded and as they melted glacial till material
trapped in the ice was deposited creating fluting,
visible on satellite images today
. As the water levels
receeded t he resulting smaller river course was a tight
loop which extended from today’s river bed around Moon
Lake and back to
today’s river bed as shown in the following "Google Earth"
view of the Moon Lake area.
The final step in the creation the creation
of Moon Lake was the erosion and deposit of sediment by the river
current. Sediment was
eroded on the outside of the river bend where the current was the
fastest and deposited on the inside of the river bend where the
current was the slowest. This continued over time until
the river created a new channel and the old river channel was
isolated from the new river channel creating the present narrow
crescent shaped lake.
An animation of river meander formation
can be found at http://www.cleo.net.uk/resources/displayframe.php?src=309/consultants_resources%2F_files%2Fmeander4.swf
The present river channel
flow follows the South-east bank of the original glacial river
basin (flowing South to North) . It provides drainage of snow melt
from the Rocky Mountains to the Hudson Bay. It is constantly changing due to
the deposits of river sand and silt. Winter freeze and thaw of ice
help to build the constantly shifting river sandbars. A strong current, unpredictable
undertows and fluctuating water levels demand respect from those
who use the river and riverbank parks for recreational
purposes.
Site Visit and Earth Cache
Logging requirements :
You are required to visit
the following location to log this
cache:
1.
The Moon Lake Golf Course (MNLKGC-PK)
located approximately 14 Km south of Saskatoon on Valley Road (west
side of the South Saskatchewan River). As you drive to this location
along Valley Road, note the flat terrain which is the glacial river
bottom. There are many
market gardens and a sod farm located in this area. Parking is available and you may
view and photograph Moon Lake from the parking lot Westerly edge.
You should also make
note of the glacial fluting visible along the Golf Course entry
drive way (MNLK-WV to MNLKGC-PK). The Golf course itself was built
utilizing the existing glacial fluting in this area. View point MNLKGC-PK is only
available during the regular golf season. Refer to
their WEB site
for information on
season dates and hours.
Note:
Winter
logging of this earth cache is possible by visiting
alternate waypoint MNLK-WV, noting/photographing the visible
glacial fluting. There is adequate room at the gates to safely stop
and complete the logging requirements (wheel chair
accessible).
Please email me the
answer to the following (do not post in your
log)
1. Using your
observed direction of the existing river flow determine the
direction of the glacial ice eddy that created the glacial fluting
(ie clock-wise or counter clock-wise)?
2. In your
opinion will the existing river loop form a smaller oxbow in the
future? Discuss your
reasoning.
Log your completion on the
geocache page and post a photograph of your choice at any of the
waypoints to share with fellow geocachers. The photo should include
you and/or your GPSr as well as the background view. Please note that photo logging is
optional but desirable.
Thank you for completing
this Earth Cache. I
hope you enjoyed the waypoint views and learned a bit more of the
South Saskatchewan River Valley Geology.
 |
All access permissions for the
listed waypoints have been obtained from the appropriate land
owner/manager. |
